Dark current is the relatively small electric current that flows though photosensitive devices even when no photons are entering the device. Dark current is one of the main sources for noise in image sensors. Dark current fixed pattern noise can be determined and recorded in advance for each individual sensor and then subtracted out during actual use of the sensor to reduce the dark current fixed pattern noise in an image. Since dark current fixed pattern noise is dependent on temperature, however, a previously recorded dark current fixed pattern noise may not be very accurate since the temperature of the sensor can vary during actual use. The sensor may be cooled to reduce the dark current fixed pattern noise, but it is not always possible or practical to include a cooling system in a device utilizing a sensor.
Embodiments of the invention address these and other issues individually and collectively.